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The manifold on this Heatec HC heater connects to four independent hot oil circuits, each with its own side pump. Independent circuits provide more operating
options than single circuits.
When water is detected it should
be purged from the system.
This can take from two hours
to two days or longer, resulting
in downtime for the heater. The
purge time depends on the
amount of heat transfer oil in
the system, the amount of water
in the oil, and how the piping
system is designed.
How Does Water Get In?
The expansion tank
accommodates expansion and
contraction of heat transfer
oil during normal operation
of the heating system. The
tank is partially filled with heat
transfer oil and is vented to the
atmosphere (the unfilled space
in the tank consists of air). As
the heat transfer oil cools, it
contracts and draws in fresh
air. The cooling process causes
moisture in the air to condense
into water, which collects in the
heat transfer oil and eventually
moves into the heating circuit.
Purging the Water
Heatec HC or HCS heaters are
designed to facilitate purging
If you increase the temperatures in
increments in excess of 10 degrees, the
expansion tank may boil over. It is also
important to make sure all the steam has
exited the overflow/vent pipe to prevent
the expansion tank from boiling over.
water from the hot oil system.
The most effective way to remove
the water from their system
is convert it to steam in the
expansion tank and allow it to
escape into the atmosphere. But
this process must be confined
to the expansion tank while
avoiding the creation of steam in
the circulating system. It requires
careful manipulation of oil
temperature and pressure.
The process of purging water
from the system includes several
steps that require the resetting
of valves on the heater to reroute
the return fluid directly through
the expansion tank. Since air in
the expansion tank is constantly
at atmospheric pressure, a
temperature of 212 degrees
Fahrenheit is all that is needed
to change water into steam so it
can escape through the overflow/
vent pipe.
It is important to create and
maintain a back pressure by
adjusting the valve at the inlet of
the expansion tank to restrict the
flow of the fluid diverted into the
tank. When doing so, be aware
that increasing system pressure
beyond its usual operating
pressure can rupture worn parts.
Always start cold and heat the
oil slowly in increments of 10
degrees to allow the water to boil
out progressively. Failure to do so
may create a violent reaction in
the expansion tank as the waterladen
heat transfer oil enters
the tank and its pressure drops
suddenly due to atmospheric
pressure.
Preventive Maintenance
Routinely purging water from
the hot oil heating system
should be part of the preventive
maintenance plan. By keeping the
system in good working order,
the heater will last longer and
cost less to operate.
FOR MORE INFORMATION
about purging water from hot oil systems at HMA plants,
call Heatec Service Manager Ron Henry
800-235-5200
Fax: 423-821-7673 • E-mail: rhenry@heatec.com
HOT-MIX MAGAZINE 32 VOLUME 16 NUMBER 1